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Pertussis
Overview

Causative Agent

  • Bordetella pertussis. B.paratussis causes parapertussis.

 

 

Incubation Period

  • 5 - 21 days (average 7 days)

 

 

Infectious Period

  • From catarrhal stage till 3 weeks after onset of typical paroxysm in patients not treated with antibiotics. If antibiotic therapy initiated, period of infectiousness is usually 5 days or less after onset of therapy. A highly contagious disease with an 80% attack rate in non-immune persons.

 

 

Transmission

Via respiratory droplets or direct contact with nasal or throat secretions of an infected person. Adolescents and adults with unrecognized pertussis are a reservoir of infection for infants and children.

 

 

Epidemiology

  • The disease is far more severe in children and may be fatal in infants. The highest incidence continues to be in infants (<6 months) who are either unimmunised or incompletely immunised with the primary course of vaccination.
  • Increasing incidence in adolescents and adults (with occasional community and school outbreaks) noted in many industrialised countries due to waning vaccine immunity. The true disease burden is however under-estimated due to low recognition, reporting and limitations in diagnostic testing.
  • In Singapore, a sharp increase in the incidence of pertussis from an annual average of 4 laboratory confirmed cases to 38 cases was reported in 2007. The highest incidence rate was observed in children under 6 months of age. Among the three major ethnic groups, Malays had the highest incidence rate followed by Chinese and Indians. Only nine cases had at least one dose of DTP vaccination prior to onset of illness.
Detection & Treatment
  • Nasopharyngeal  swabs (use Dacron) for culture or PCR assay.
  • Fastidious  organism requiring special media for culture. Highest yield if performed within  3 weeks of cough onset or 4 weeks of symptom onset. Sensitivity and specificity  of culture and PCR negatively affected by delayed transport to laboratory,  vaccination, recent antibiotic use and prolonged illness. Culture remains the  gold standard but suffers from low sensitivity. PCR-based assays increasingly  used and may be more sensitive.
  • Serology  for pertussis toxin (PT) IgG or IgA performed in acute and convalescent  specimens may support the diagnosis. A single high titer may be indicative of  recent infection (e.g. >100U/ml anti-PT IgG). 
Care Management
  • Empiric  treatment recommended if the diagnosis is strongly suspected.
  • Respiratory  isolation for known cases. Suspect cases should be removed from the presence of  young children and non-immunized infants until patients have received at least  5 days of antibiotics. 
  • Antibiotic treatment unlikely to shorten duration of illness if  started more than one week after symptom onset, but is beneficial in shortening  the infectious period and decreasing transmission.
  • In  vitro, most strains are sensitive to both macrolides and fluoroquinolones, but  resistant to beta-lactams. Limited clinical experience with fluoroquinolones.
  • Macrolides  are the recommended first line of therapy. For adults and adolescents:    
  • Infection  in infants under age 6 months may require hospitalization due to complications  of hypoxemia, apnoea or poor feeding.

 

 

Management of close contacts

  • Administer  antibiotic chemoprophylaxis if within 3 weeks of exposure.
  • Use  same drugs and duration as for treatment (see Management above).
  • Review  pertussis vaccination status of all contacts especially infants or adults  caring for infants to ensure currency.
  • Evidence  for post-exposure immunization to prevent infection is limited. 
This page was last updated in 2026.